Hydraulic valves for pivot motor adjustment devices of a camshafts are well known in the art. Hydraulic valves include a valve piston that is axially moveable in a valve housing of the hydraulic valve. Typically the valve housing includes a first operating connection, a second operating connection and a supply connection. The first operating connection and the second operating connection are connected with the pivot motor adjustment device and a hydraulic fluid is feedable through these connections into the hydraulic valve and also from the hydraulic valve. In order to supply the hydraulic valve with the hydraulic fluid that is fed by a feed device the valve housing includes the supply connection. The hydraulic fluid can flow through the hydraulic valve in different paths controlled by a flowable channel system of the valve piston. In order to use a camshaft adjustment torques the hydraulic valve includes at least one check valve in the portion of the operating connections. Additionally a check valve is arranged in a flow portion of the supply connection. Thus, the check valves facilitate controlling the hydraulic fluid in the hydraulic valve as a function of a pressure.
Check valves for hydraulic valves whose closure elements are configured band shaped are also known. This can be derived from the French patent document FR 525 481 published in 1921 which discloses a check valve including a band shaped closure element.
The patent document DE 101 43 433 B4 discloses a band shaped closure element of a hydraulic valve wherein the closure element includes spring supported closure flaps.
A band shaped closure element of a check valve for a hydraulic valve can also be derived from the patent document EP 2 503 201 B1. The disclosed closure valve is characterized in that it includes a stop at a band end in order to limit its expansion. Since the closure element is only flowable within limits due to the stop different types of flow openings are provided.
The publication document US 2013 206 088 A1 discloses a hydraulic valve whose check valve is provided with a spring based closure element and received in the valve piston.
By the same token check valves with a band shaped closure elements for pivot motor adjustment devices for camshafts are known. The publication documents DE 10 2010 061 337 A1 and DE 10 2010 019 004 A1 disclose hydraulic valves with a band shaped closure element of the check valve. Contrary to the hydraulic valve known from DE 10 2010 061 337 A1 which respectively uses a check valve for the first operating connection and the second operating connection the hydraulic valve disclosed in DE 10 2010 019 004 A1 includes a single check valve through which the first operating connection and the second operating connection can be loaded as a function of a positioning of the valve piston that is axially moveable in the valve housing of the hydraulic valve along a longitudinal axis of the valve housing. The operating connection and the second operating connection are thus axially offset from one another wherein the supply connection of the valve housing is arranged between the first operating connection and the second operating connection. In order to flow the hydraulic valve through ring grooves in the valve housing are associated with the connections.
The check valve is arranged at the valve piston in a positioning groove of the valve piston that is oriented towards the ring grooves wherein the positioning groove is connected with the channel system in a flowable manner wherein the valve piston is moveable in the valve housing. Due to the axial move ability of the valve piston there is an option to use the first check valve for both operating connections.
The hydraulic fluid can flow through the hydraulic valve on different paths determined by the flowable channel system wherein a first tank connection of the hydraulic valve is configured at the valve housing providing a drain for the hydraulic fluid out of the hydraulic valve.
In order to quickly adjust the camshaft a quick and unimpeded response of the hydraulic valve, put differently a quick axial movement of the valve piston in the valve housing is required. Thus, it is necessary that the closure element of the check valve does not contact the valve housing during operations of the pivot motor adjustment device.